Optical glass for polarizing optical system, production process therefor and polarizing beam splitter

Abstract

An optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10 −8 cm 2 /N] with respect to a wavelength of 633 nm, the optical glass having the following composition (1): composition (1): when represented in terms of wt. % of oxides: SiO 2 : 17.0-27.0% (35.5-57.0 mol %) Li 2 O+Na 2 O+K 2 O: 0.5-5.0% (0.7-20.0 mol %) PbO: 72.0-75.0% (39.1-45.0 mol %) As 2 O 3 +Sb 2 O 3 : 0.1-3.0% (0.1-2.0 mol %).

What is claimed is:  
     
       1. An optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10 −8  cm 2 /N] with respect to a wavelength of 633 nm, the optical glass having the following composition (1): 
       composition (1): when represented in terms of wt. % of oxides:  
       SiO 2 : 17.0-27.0% (35.5-57.0 mol %)  
       Li 2 O+Na 2 O+K 2 O: 0.5-5.0% (0.7-20.0 mol %)  
       PbO: 72.0-75.0% (39.1-45.0 mol %)  
       As 2 O 3 +Sb 2 O 3 : 0.1-3.0% (0.1-2.0 mol %).  
     
     
       2. An optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10 −8  cm 2 /N] with respect to a wavelength of 633 nm, the optical glass having the following composition (2): 
       composition (2): when represented in terms of mol %:  
       SiO 2 : 40.0-54.0 mol %  
       R 2 O (R: alkali metal): 0.5-9.0 mol %  
       PbO: 43.0-45.5 mol %  
       As 2 O 3 +Sb 2 O 3 : 0.1-1.5 mol %; and  
       the composition (2) further containing fluorine in the following range when represented in terms of mol %:  
       fluorine/oxygen (F/O) ratio: 0.1-18.0.  
     
     
       3. An optical glass for polarizing optical system having a photoelastic constant C in the range of −0.2 to +0.5 [10 −8  cm 2 /N] with respect to a wavelength of 633 nm, the optical glass having the following composition (3): 
       composition (3) when represented in terms of mol %:  
       SiO 2 : 40.0-54.0 mol %  
       R 2 O (R: alkali metal): 0.5-9.0 mol %  
       RF: 0-16.0 mol %  
       R 2 SiF 6 : 0-3.3 mol %  
       PbO+PbF 2 : 43.0-45.5 mol %  
       PbF 2 : 0-10.0 mol %  
       As 2 O 3 +Sb 2 O 3 : 0.1-1.5 mol %; and  
       the composition (3) further containing fluorine in the following range in terms of mol %:  
       fluorine/oxygen (F/O) ratio: 0.1-18.0.